The present invention is in a glass melting furnace in which a mixture, or batch, is fed at a narrow side of a rectangular glass melting tank onto the molten glass mass (or bath) across the full width thereof. The furnace includes burners positioned adjacent to the opposite narrow side for supplying energy, and heat exchangers for energy exchange between the combustion exhaust gases and the combustion air supplied to the burners. The exhaust gas openings are disposed adjacent to the mixture feeding area. The invention is also in a method of operating such a glass melting furnace.
Even when operated with recuperators or regenerators, glass melting furnaces generally suffer from the drawback of a relatively low efficiency. This is due not only to the lack of insulation of the glass tanks, but also due to the fact that the thermal energy of the exhaust gas heat is considerably higher than that required to preheat the combustion air. Here, limits exist with respect to increasing the temperature of the combustion air, because in such a case the heat exchange becomes very complex and the concentration of the poisonous NO.sub.x greatly increases.
Various attempts have been made to utilize expediently the excess heat in the exhaust gas, such as by preheating the mixture, or bath, prior to its feeding into the glass melting tank. However, these attempts proved unsuccessful for a number of reasons. It was found that such preheating may result in premelting of certain constituents of the mixture and such constituents tended to stick to the heat exchanging surfaces. It was also found that unmixing occurs under a direct contact of the exhaust gas with the mixture, or certain constituents of the mixture were carried over or entrained such that the dust concentration increased significantly in the exhaust gas. This resulted in expensive dust removal requirements.